Visual Studio Online Service Down Today

This is the first time I meet Microsoft Visual Studio Online Service down, I could not connect to my VS Online Projects, they might call it is User Hub. Some of my source code are on VS Online.

When I tried to login the VS Online account, I could access Visualstudio.com home page without problem, but could not access user hub, got the following error sometimes, or just a timeout message:

VS400664: Sorry, we were unable to retrieve a configured identity provider for you to use when creating an account. If the problem persists, check your web browser security settings. You may need to add https://tfsprodch1acs01.accesscontrol.windows.net to your trusted zones.